Preparation of anhydride-capped polyphenylene ether in a melt process

ABSTRACT

Polyphenylene ethers are capped by reaction in the melt, with application of vacuum, with at least one trimellitamide, preferably phenyl 4-aminosalicylate trimellitamide. The preferred melt processing method is extrusion with vacuum venting. By this method, the polyphenylene ether is capped with reactive anhydride groups improving its thermo-oxidative stability. The capped polyphenylene ether is capable of forming copolymers with polyamides, and said copolymers are useful as compatibilizers for polyphenylene ether-polyamide blends.

This invention relates to polyphenylene ethers and more particularly to their functionalization with trimellitamides.

Polyphenylene ethers are a well-known class of polymers characterized by a unique combination of chemical, physical and electrical properties over a temperature range of more than 350° C. extending from a brittle point of about -170° C. to a heat distortion temperature of 190° C. This combination of properties renders them suitable for use as engineering thermoplastics in a broad range of applications which are well known in the art and are disclosed in numerous patents and other publications.

In recent years, there has been considerable interest in combining polyphenylene ethers with other resins to produce compositions with even more advantageous properties. For example, polymers such as polyamides are frequently noted for their solvent resistance and blends of such polymers with polyphenylene ethers might be expected to possess the advantageous properties of the latter and in addition be highly resistant to solvents. However, simple blends of polyphenylene ethers and polyamides are generally incompatible, frequently undergoing phase separation and delamination. They typically contain large, incompletely dispersed polyphenylene ether particles and no phase interaction between the two resin phases.

U.S. Pat. No. 4,642,358 describes the reaction of polyphenylene ethers with such polycarboxylic reactants as trimellitic anhydride acid chloride (TAAC).

A disadvantage of the reaction of polyphenylene ethers with TAAC is that it must be conducted in solution, typically in an organic solvent such as toluene. Polyphenylene ethers are often melt processed rather than solution processed, in which case the requirement of solution functionalization is undesirable. Moreover, the products prepared by this method frequently coagulate, contain large proportions of fines and have substantial chloride content. All of these conditions may be disadvantageous for many utilities of the resulting blends.

In U.S. Pat. No. 4,808,671, there is described the reaction of polyphenylene ethers with 4-esters of trimellitic anhydride in the presence of a catalytic amount of at least one triaryl phosphite. This process may be conducted in the melt and may utilize such trimellitic acid esters as the 4-(o-carbophenoxyphenyl) ester, also known as the 4(phenylsalicylate) ester, of trimellitic anhydride. Esters of this type react with polyphenylene ethers in two ways: by functionalizing it with functionality derived from the 4-ester of trimellitic anhydride and by capping unfunctionalized molecules with salicylate in accordance with U.S. Pat. No. 4,760,118. The disadvantage of this method is the requirement for triaryl phosphite catalysis in order to promote complete reaction. In the absence of triaryl phosphite, the functionalization reaction is incomplete and substantial proportions of residual trimellitic anhydride 4-ester may remain in the production, with possible detrimental results.

U.S. Pat. No. 4,988,775 discloses a method of producing a dicarboxylate-capped polyphenylene ether capable of forming blends with polyamides having high impact and tensile strength. The above-mentioned dicarboxylate-capped polyphenylene ethers are prepared by melt blending with application of vacuum at least one polyphenylene ether with at least one trimellitic anhydride salicylate ester.

The present invention provides an economic and convenient method for incorporating anhydride functionality into the polyphenylene ether resin at its phenolic end groups. This process is faster and more selective than the above mentioned transesterification process. The process of the present invention is believed to afford a single cap on the polyphenylene ether, whereas the above mentioned dicarboxylate polyphenylene ethers is believed to have both salicylate and TAAC capping. The present invention may provide polyphenylene ethers with a low total hydroxyl content and hence greatly improved thermo-oxidative stability.

Therefore the present invention provides a trimellitamide capped polyphenylene ether composition prepared by melt blending, with application of vacuum, at least one polyphenylene ether with at least one trimellitamide selected from the group consisting of phenyl 4-aminosalicylate trimellitamide, acetyl 4-aminosalicylic acid trimellitamide and acetyl 5-aminosalicylic acid trimellitamide.

The trimellitamides useful in the present invention are prepared by the reaction of their respective aminosalicylic acids with trimellitic anhydride acid chloride.

The melt blending operation may be performed in conventional melt blending apparatus of both the batch and continuous type. It is often preferably conducted continuously in an extruder, by reason of the excellent properties of extruded materials and the availability of extruders in commercial polymer processing facilities. Typical conditions include temperatures in the range of about 250° C. to about 350° C. The proportion of trimellitamide employed is not critical and will depend on the degree of capping desired. It is most often about 2-3% but may be as high as about 10% by weight based on polyphenylene ether.

It is essential that the blending be conducted with application of vacuum. In general, blending processes involving pressures below about 20 torr for at least a portion of the process are desirable. Extrusion processes of this type may be conducted by means of vacuum venting, whereby a vacuum is drawn on at least one vent in the extruder.

It has been found that reaction between the polyphenylene ether and the trimellitamide is facilitated if the polyphenylene ether has also been melt processed under vacuum prior to formation of the blend with the amide. This melt processing operation may also be conveniently effected via extrusion with vacuum venting. Polyphenylene ether-polyamide compositions prepared from the dicarboxylate-capped polyphenylene ethers of the invention are generally improved in several respects by repeated extrusion of the capped polyphenylene ether. Optimum conditions are often provided if the capped polyphenylene ether is again melt processed (e.g., extruded) at least once, also under vacuum.

In addition, the properties of polyphenylene ether-polyamide compositions prepared from the dicarboxylate-capped polyphenylene ethers of the invention are generally improved in several respects by repeated extrusion of the capped polyphenylene ether. Optimum conditions are often provided if the capped polyphenylene ether is again melt processed (e.g., extruded) at least once, also under vacuum.

It is believed that the present invention produces capped polypheylene ethers by the following mechanism. It is thought that under thermal conditions the trimellitamide may form a molecule of the following formula: ##STR1## or an analogous structure, thus forming an extremely electrophilic ketene. It is further believed that the polyphenylene ether is capped by addition at the carbon of the ketene.

The polyphenylene ethers used in the present invention comprise a plurality of structural units having the formula ##STR2##

In each of the units independently, each Q¹ is independently halogen, primary or secondary lower alkyl (i.e., alkyl containing up to 7 carbon atoms), phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy or halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms; and each Q² is independently hydrogen, halogen, primary or secondary lower alkyl, phenyl, haloalkyl, hydrocarbonoxy or halohydrocarbonoxy as defined for Q¹ . Examples of suitable primary lower alkyl groups are methyl, ethyl, n-propyl, n-butyl, isobutyl, n-amyl, isoamyl, 2-methylbutyl, n-hexyl, 2,3-dimethylbutyl, 2-, 3- or 4-methylpentyl and the corresponding heptyl groups. Examples of secondary lower alkyl groups are isopropyl, sec-butyl and 3-pentyl. Preferably, any alkyl radicals are straight chain rather than branched. Most often, each Q¹ is alkyl or phenyl, especially C₁ -C₄ alkyl and each Q² is hydrogen. Suitable polyphenylene ethers are disclosed in a large number of patents.

Both homopolymer and copolymer polyphenylene ethers are included. Suitable homopolymers are those containing 2,6-dimethyl-1,4-phenylene ether units. Suitable copolymers include random copolymers containing such units in combination with (for example) 2,3,6-trimethyl-1,4-phenylene ether units.

Also included are polyphenylene ethers containing moieties which modify properties such as molecular weight, melt viscosity and/or impact strength. Such polymers may be prepared by grafting onto the polyphenylene ether such vinyl monomers as acrylonitrile and vinylaromatic compounds (e.g., styrene), or such polymers as polystyrenes and elastomers. Other suitable polymers are the coupled polyphenylene ethers in which the coupling agent is reacted with the hydroxy groups of two polyphenylene ether chains to produce a higher molecular weight polymer containing the reaction product of the hydroxy groups and the coupling agent, provided a substantial proportion of free hydroxy groups remain present. Illustrative coupling agents are low molecular weight polycarbonates, quinones and heterocycles.

The polyphenylene ether generally has a number average molecular weight within the range of about 3,000 to 40,000 and a weight average molecular weight within the range of 20,000-80,000 as determined by gel permeation chromatography. Its intrinsic viscosity is most often in the range of about 0.15 dl./g. to about 0.6 dl./g., as measured in chloroform at 25° C.

The polyphenylene ethers are typically prepared by the oxidative coupling of at least one corresponding monohydroxyaromatic compound. Particularly useful and readily available monohydroxyaromatic compounds are 2,6-xylenol (wherein each Q¹ is methyl and each Q² is hydrogen), whereupon the polymer may be characterized as a poly(2,6-dimethyl-1,4-phenylene ether) and 2,3,6-trimethylphenol (wherein each Q¹ and one Q² is methyl and the other Q² is hydrogen).

A variety of catalyst systems are known for the preparation of polyphenylene ethers by oxidative coupling. There is no particular limitation as to catalyst choice and any of the known catalysts can be used. For the most part, they contain at least one heavy metal compound such as a copper, manganese or cobalt compound, usually in combination with various other materials.

A first class of preferred catalyst systems consists of those containing a copper compound. Such catalysts are disclosed, for example, in U.S. Pat. Nos. 3,306,874, 3,306,875, 3,914,266 and 4,028,341. They are usually combinations of cuprous or cupric ions, halide (i.e., chloride, bromide or iodide) ions and at least one amine.

Catalyst systems containing manganese compounds constitute a second preferred class. They are generally alkaline systems in which divalent manganese is combined with such anions as halide, alkoxide or phenoxide. Most often, the manganese is present as a complex with one or more complexing and/or chelating agents such as dialkylamines, alkanolamines, alkylenediamines, o-hydroxyaromatic aldehydes, o-hydroxyazo compounds, hydroxyoximes (monomeric and polymeric), o-hydroxyaryl oximes and β-diketones. Also useful are known cobalt-containing catalyst systems. Suitable manganese and cobalt-containing catalyst systems for polyphenylene ether preparation are known in the art by reason of disclosure in numerous patents and publications.

Particularly useful polyphenylene ethers for the purposes of this invention are those which comprise molecules having at least one of the end groups of the formulas ##STR3## wherein Q¹ and Q² are as previously defined; each R² is independently hydrogen or alkyl with the proviso that the total number of carbon atoms in both R² radicals is 6 or less; and each R³ is independently hydrogen or a C₁₋₆ primary alkyl radical. Preferably, each R² is hydrogen and each R³ is alkyl, especially methyl or n-butyl.

Polymers containing the aminoalkyl-substituted end groups of formula II may be obtained by incorporating an appropriate primary or secondary monoamine as one of the constituents of the oxidative coupling reaction mixture, especially when a copper- or manganese-containing catalyst is used. Such amines, especially the dialkylamines and preferably di-n-butylamine and dimethylamine, frequently become chemically bound to the polyphenylene ether, most often by replacing one of the hydrogen atoms on one or more Q¹ radicals. The principal site of reaction is the Q¹ radical adjacent to the hydroxy group on the terminal unit of the polymer chain. During further processing and/or blending, the aminoalkyl-substituted end groups may undergo various reactions, probably involving a quinone methide-type intermediate of the formula ##STR4## with numerous beneficial effects often including an increase in impact strength and comparibilization with other blend components. Reference is made to U.S. Pat. Nos. 4,054,553, 4,092,294, 4,477,649, 4,477,651 and U.S. Pat. No. 4,517,341, the disclosures of which are incorporated by reference herein.

Polymers with 4-hydroxybiphenyl end groups of formula VI are typically obtained from reaction mixtures in which a by-product dipehnoquinone of the formula ##STR5## is present, especially in a copper-halide-secondary or tertiary amine system. In this regard, the disclosure of U.S. Pat. No. 4,477,649 is again pertinent as are those of U.S. Pat. No. 4,234,706 and U.S. Pat. No. 4,482,697, which are also incorporated by reference herein. In mixtures of this type, the dipehnoquinone is ultimately incorporated into the polymer in substantial proportions, largely as an end group.

In many polyphenylene ethers obtained under the above-described conditions, a substantial proportion of the polymer molecules, typically constituting as much as about 90% by weight of the polymer, contain end groups having one or frequently both of formulas II and III. It should be understood, however, that other end groups may be present and that the invention in its broadest sense may not be dependent on the molecular structures of the polyphenylene ether end groups.

It will be apparent to those skilled in the art from the foregoing that the polyphenylene ethers contemplated for use in the present invention include all those presently known, irrespective of variations in structural units of ancillary chemical features.

The trimellitamide-capped polyphenylene ethers of the present invention are useful in the preparation of compatibilized blends of polyphenylene ethers and polyamides. In particular, the capped polyphenylene ethers form copolymers with polyamides, which may be used for compatibilization of such blends. Compositions comprising such polyphenylene ether-polyamide copolymers are disclosed and claimed in commonly owned, copending application Ser. No. 07-660368, filed Feb. 25, 1991.

Polyamides suitable for use in the preparation of the compositions of this invention may be made by any known method, including the polymerization of a monoaminomonocarboxylic acid or a lactam thereof having at least 2 carbon atoms between the amino and carboxylic acid or a lactam thereof as defined above together with substantially equimolar proportions of a diamine and a dicarboxylic acid. (the term "substantially equimolar" proportions includes both strictly equimolar proportions and slight departures therefrom which are involved in conventional techniques for stabilizing the viscosity of the resultant polyamides.) The dicarboxylic acid may be used in the form of a functional derivative thereof, for example, an ester or acid chloride.

Examples of the aforementioned monoaminomonocarboxylic acids or lactams thereof which are useful in preparing the polyamides include those compounds containing from 2 to 16 carbon atoms between the amino and carboxylic acid groups, said carbon atoms forming a ring with the --CO-- NH- group in the case of a lactam. Particular examples of aminocarboxylic acids and lactams are ε-aminocaproic acid, butyrolactam, pivalolcatam, ε-caprolactam, capryllactam, enantholactam, undecanolactam, dodecanolactam and 3- and 4-aminobenzoic acids.

Diamines suitable for use in the preparation of the polyamides include the straight chain and branched chain alkyl, aryl and alkaryl diamines. Such diamines include, for example, those represented by the general formula

    H.sub.2 N(CH.sub.2).sub.n NH.sub.2

wherein n is an integer of from 2 to 16. Illustrative diamines are trimethylenediamine, tetramethylenediamine, pentamethylenediamine, octamethylenediamine, hexamethylenediamine (which is often preferred), trimethylhexamethylenediamine, m-phenylenediamine and mxylylenediamine.

The dicarboxylic acids may be represented by the formula

    HOOC--W--COOH

wherein W is a divalent aliphatic or aromatic group containing at least 2 carbon atoms. Examples of aliphatic acids are sebacic acid, octadecanedioic acid, suberic acid, glutaric acid, pimelic acid and adipic acid. Aromatic acids, such as isophthalic and terephthalic acids, are preferred.

Typical examples of the polyamides or nylons, as these are often called, include polyamide-6, 66, 11, 12, 63, 64, 6/10 and 6/12 as well as polyamides from terephthalic acid and/or isophthalic acid and trimethylhexamethylenediamine; from adipic acid and mxylylenediamines; from adipic acid, azelaic acid and 2,2-bis(p-aminocyclohexyl)propane and from terephthalic acid and 4,4'-diaminodicyclohexylmethane. Mixtures and/or copolymers of two or more of the foregoing polyamides or prepolymers thereof, respectively, are also within the scope of the present invention. Preferred polyamides are polyamide-6, 66, 11 and 12, most preferably polyamide-66.

Copolymer formation according to the invention is believed to be the result of reaction between the dicarboxylate end groups of the polyphenylene ether and amine groups in the polyamide, forming imide linkages. Accordingly, the presence of a substantial proportion of amine end groups in the polyamide is preferred. If such amine end groups are not present in substantial proportion, partial degradation of the polyimide is necessary to enable the formation of the desired copolymers.

To prepare the copolymer compositions, the dicarboxylate-capped polyphenylene ether and polyamide are heated together in solution or, preferably, in the melt. Here, as in the operations previously described, melt processing under vacuum is especially preferred and extrusion with vacuum venting is most preferred. The reaction temperature is typically within the range of about 100°-350° C.

The proportions of functionalized polyphenylene ether and polyamide are not critical and may be adjusted over a wide range to yield copolymer compositions having the desired properties. The polyphenylene ether-polyamide compositions, however, generally contain about 5-75% by weight polyphenylene ether and about 25-95% polyamide.

In general, the compositions of this invention comprise only partially copolymer, with the balance being a polyphenylene ether-polyamide blend. It is also within the scope of the invention to incorporate uncapped polyphenylene ether in the composition, said uncapped polyphenylene ether frequently comprising up to about 50% by weight of total polyphenylene ether. In general, however, optimum properties are obtained when no uncapped polyphenylene ether is separately added.

The polyphenylene ether-polyamide compositions of this invention may also contain ingredients other than the copolymer, polyphenylene ether and polyamide. A particularly useful other ingredient in many instances is at least one elastomeric impact modifier which is compatible with the polyphenylene ether. It is generally present in the amount of about 5-25% by weight of resinous components.

Impact modifiers for polyphenylene ether-polyamide compositions are well known in the art. They are typically derived from one or more monomers selected from the group consisting of olefins, vinyl aromatic monomers, acrylic and alkylacrylic acids and their ester derivatives as well as conjugated dienes. Especially preferred impact modifiers are the rubbery high-molecular weight materials including natural and synthetic polymeric materials showing elasticity at room temperature. They include both homopolymers and copolymers, including random, block, radial block, graft and core-shell copolymers as well as combinations thereof.

A particularly useful class of impact modifiers are those derived from the vinyl aromatic monomers. These include, for example, modified and unmodified polystyrenes, ABS type graft copolymers, AB and ABA type block and radial block copolymers and vinyl aromatic conjugated diene core shell graft copolymers. Modified and unmodified polystyrenes include homopolystyrenes and rubber modified polystyrenes, such as butadiene rubber-modified polystyrene (otherwise referred to as high impact polystyrene or HIPS). Additional useful polystyrenes include copolymers of styrene and various monomers, including, for example, poly (styreneacrylonitrile) (SAN), styrene-butadiene copolymers as well as the modified alpha- and para-substituted styrenes and any of the styrene resins disclosed in U.S. Pat. No. 3,383,435, herein incorporated by reference. ABS types of graft copolymers are typified as comprising a rubber polymeric backbone derived from a conjugated diene alone or in combination with a monomer copolymerizable therewith having grafted thereon at least one monomer, and preferably two, selected from the group consisting of monoalkenylarene monomers and substituted derivatives thereof as well as acrylic monomers such as acrylonitriles and acrylic and alkylarcrylic acids and their esters.

As especially preferred subclass of vinyl aromatic monomer-derived resins is the block copolymers comprising monoalkenyl arene (usually styrene) blocks and conjugated diene (e.g., butadiene or isoprene) blocks and represented as AB and ABA block copolymers. The conjugated diene blocks may be selectively hydrogenated.

Suitable AB type block copolymers are disclosed in, for example, U.S. Pat. Nos. 3,078,254; 3,402,159; 3,297,793; 3,265,765 and 3,594,452 and UK Patent 1,264,741, all incorporated herein by reference. Examples of typical species of AB block copolymers are polystyrene-polybutadiene (SRB), polystyrene-polyisoprene and poly (alpha-methylstyrene)-polybutadiene. Such AB block copolymers are available commercially from a number of sources, including Phillips Petroleum under the trademark SOLPRENE.

Additionally, ABA triblock copolymers and processes for their production as well as hydrogenation, if desired, are disclosed in U.S. Pat. Nos. 3,149,182; 3,231,635; 3,462,162; 3,287,333; 3,595,942; 3,694,523 and U.S. Pat. No. 3,842,029, all incorporated herein by reference.

Examples of triblock copolymers include polystyrene-polybutadiene-polystyrene (SBS), polystyrenepolyisoprene-polystyrene (SIS), poly(a-methylstyrene)polybutadiene-poly-(a-methylstyrene) and poly(amethylstyrene)-polyisoprene-poly-(a methylstyrene). Particularly preferred triblock copolymers are available commercially as CARIFLEX˜, KRATON D˜ and KRATON G˜ from Shell.

Another class of impact modifiers is derived from conjugated dienes. While many copolymers containing conjugated dienes have been discussed above, additional conjugated diene modifier resins include, for example, homopolymers and copolymers of one or more conjugated dienes including, for example, polybutadiene, butadiene-styrene copolymers, butadiene-glycidyl methacrylate copolymers, isoprene-isobutylene copolymers, chlorobutadiene polymers, butadiene-acrylonitrile copolymers, polyisoprene, and the like. Ethylene-propylene-diene monomer rubbers may also be used. These EPDM'S are typified as comprising predominantly ethylene units, a moderate amount of propylene units and up to about 20 mole percent of non-conjugated diene monomer units. Many such EPDM's and processes for the production thereof are disclosed in U.S. Pat. Nos. 2,933,480; 3,000,866; 3,407,158; 3,093,621 and U.S. Pat. No. 3,379,701, incorporated herein by reference.

Other suitable impact modifiers are the core-shell type graft copolymers. In general, these have a predominantly conjugated diene rubbery core or a predominantly cross-linked acrylate rubbery core and one or more shells polymerized thereon and derived from monoalkenylarene and/or acrylic monomers alone or, preferably, in combination with other vinyl monomers. Such core-shell copolymers are widely available commercially, for example, from Rohm and Haas Company under the trade names KM611, KM-653 and KM-330, and are described in U.S. Pat. Nos. 3,808,180; 4,034,013; 4,096,202; 4,180,494 and U.S. Pat. No. 4,292,233.

Also useful are the core-shell copolymers wherein an interpenetrating network of the resins employed characterizes the interface between the core and shell. Especially preferred in this regard are the ASA type copolymers available from General Electric Company and sold as GELOY˜ resin and described in U.S. Pat. No. 3,944,631.

In addition, there may be employed the above described polymers and copolymers having copolymerized therewith or grafted thereon monomers having functional groups and/or polar or active groups. Finally, other suitable impact modifiers include Thiokol rubber, polysulfide rubber, polyurethane rubber, polyether rubber (e.g., polypropylene oxide), epichlorohydrin rubber, ethylenepropylene rubber, thermoplastic polyester elastomers and thermoplastic etherester elastomers.

The preferred impact modifiers are block (typically diblock, triblock or radial teleblock) copolymers of alkenylaromatic compounds and olefins or dienes. Most often, at least one block is derived from styrene and at least one other block from at least one of butadiene, isoprene, ethylene and butylene. Especially preferred are the triblock copolymers with polystyrene end blocks and olefin- or dienederived midblocks. When one of the blocks is derived from three or more dienes, it is frequently advantageous to reduce the aliphatic unsaturation therein by selective hydrogenation. The weight average molecular weights of the impact modifiers are typically in the range of about 50,000-300,000. Block copolymers of this type are commercially available from Shell Chemical Company under the trademark KRATON, and include KRATON D1101, G1650, G1651, G1652, G1657 and G1702.

Other conventional ingredients which may be present in the copolymer-containing compositions of this invention include fillers, flame retardants, colorants, stabilizers, antistatic agents, mold release agents and the like, used in conventional amounts. The presence of other resinous components is also contemplated.

In order that those skilled in the art may be better able to practice the present invention, the following examples are given as illustrations of the preparation of the trimellitamides as well as the trimellitamide functionalized polyphenylene ether of the present invention. It should be noted that the invention is not limited to the specific details embodied in the examples.

EXAMPLE 1 Preparation of Phenyl 4-Aminosalicylic Acid Trimellitamide

A THF (lL) solution of trimellitic anhydride acid chloride (115.0 g, 0.546 mol,) in a 2500 mL round-bottomed flask equipped with a mechanical stirrer, thermometer, and condenser with nitrogen inlet was cooled in an ice-water bath to ˜0° C. Phenyl 4-aminosalicylate (phenyl PAS, 125.2 g, 0.546 mol) was added to the reaction mixture as a solid in ˜10 g portions over a period of 1 hrs. The reaction mixture was allowed to warm to room temperature over a period of 3 hrs. at which time it was poured into 3.0 L hexane to precipitate a solid. The pale yellow solid was collected by filtration, washed with additional hexane, and dried in vacuo. Recrystallization from glacial acetic acid (1.0 L) afforded 346.8 g (86% yield) of phenyl 4-aminosalicylate trimellitamide as a pale yellow crystalline solid: mp: 234°-235° C. Fourier transform infra red spectroscopy (IR) (KBr) showed peaks at 1856, 1779, 1723, 1685 cm⁻¹.

EXAMPLE 2 Preparation of Acetyl 4-Aminosalicylic Acid Trimellitamide

To a THF (300mL) solution of trimellitic anhydride acid chloride (57.5 g, 0.273 mol) in a 500 mL round-bottom flask equipped with a mechanical stirrer, thermometer, and

condenser with nitrogen inlet cooled in an ice-water bath to ˜0° C. was added 4-aminosalicylate acid (41.8 g, 0.273 mol). The reaction mixture was stirred at ˜0° C. for 2 hrs. before the ice-water bath was removed and the mixture allowed to warm to room temperature. The mixture was poured into 500 mL hexane to precipitate a pale yellow solid that was collected by filtration, washed with additional hexane, and dried in vacuo. Yield: 84.5 g (95% of theoretical). mp: >280° C.

Crude 4-aminosalicylic acid trimellitamide was acetylated in the following manner: 12.5 g (38.2 mmol) of the pale yellow solid isolated as described above was refluxed in 150 mL glacial acetic acid and 45 mL acetic anhydride containing 1 mL pyridine. The initial suspension became a colorless, clear solution after 30 min at reflux temperature. At 12 hrs. reflux, the reaction mixture was cooled to room temperature. A white crystalline solid was collected by filtration, washed with cold acetic acid, and dried in vacuo at 80° C. Yield: 11.5 g (82% yield). mp: 250-251° C. IR (KBr) 1661, 1710, 1778, 1852 cm⁻¹.

EXAMPLE 3 Preparation of Acetyle 5-Aminosalicylic Acid Tremellitamide

To a THF (500mL) solution of trimellitic anhydride acid chloride (57.5 g, 0.273 mol) in a 1 L round-bottom flask equipped with a mechanical stirrer, thermometer, and condenser with nitrogen inlet cooled in an ice-water bath to ˜0° C. was added 5-aminosalicylate acid (41.8 g, 0.273 mol). An additional 200 mL THF was added to solubilize the 5-aminosalicylic acid. The reaction mixture was allowed to warm to room temperature slowly over a period of 3 hrs. before being poured into 1.5 L hexane. A pale yellow-green solid was collected by filtration, washed with additional hexane, and dried in vacuo. Yield: 91.6 g (quantitative yield). mp: 280° C.

Crude 5-aminosalicylate trimellitamide was acetylated in the following manner: 79.0 g (0.241 mol) of the solid isolated as described above was refluxed in 600 mL glacial acetic acid and 280 mL acetic anhydride containing 8 mL pyridine. The initial suspension became a colorless, clear solution after 30 min at reflux temperature. At 15 hrs. reflux, the reaction mixture was cooled to room temperature. A white crystalline solid was collected by filtration, washed with cold acetic acid, and dried in vacuo at 80° C. Yield: 30.1 g (34% yield). mp: 245°-246° C. IR (KBr) 1665, 1720, 1772, 1855 cm⁻¹.

EXAMPLE 4 Extruder Functionalization of Polyphenylene Ether Resin

Commercial PPO powder ([n]0.42 dl/g, 0.1079% OH) and phenyl 4-aminosalicylate trimellitamide (2, 2.5, or 3 weight % relative to polyphenylene ether were dry-blended in a Henschel mill until homogeneous then extruded through a Werner & Pfleiderer 28 mm twin screw extruder (PPO devol. screw design, screw speed 300 rpm, throughput 8.0-11.5 lbs/hrs., temperature profile 180°, 290°, 290°, 290°, 290°, 300° C. (die) with vacuum venting applied to zone 5. The polyphenylene ether extrudate was quenched in water and pelletized.

A small portion of pellets (˜5 g) from each extrusion was dissolved in hot toluene, precipitated by addition of acetonitrile-acetone (2:1). The polyphenylene ether was filtered, washed with acetonitrile-acetone, and dried at 80° C. (25 mm) for a minimum of 15 hrs. Acetonitrileacetone precipitation was used for samples to be submitted for FTIR analysis so that the anhydride groups bound to PPO remained intact.

The precipitated polyphenylene ether was analyzed by FTIR by measuring the absorbance of 2.5% (w/v) solution in carbon disulfide against a 2.5% (w/v) solution of completely acetate-capped polyphenylene ether. Carbonyl analysis (2.5% (w/v) carbon disulfide solution) was performed using the extinction coefficients calculated for phenyl 4-aminosalicylate trimellitamide and expressed as equivalents carbonyl per polyphenylene ether chain.

Obviously, other modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that changes may be made in particular embodiments of the invention described which are within the full intended scope of the invention as defined by the claims. It is to be further understood that all patents mentioned above are to be incorporated herein by reference. 

What is claimed is:
 1. A trimellitamide-capped polyphenylene ether composition prepared by melt blending, with application of vacuum, at least one polyphenylene ether with at least one trimellitamide selected from the group consisting of phenyl 4-aminosalicylate trimellitamide, acetyl 4-aminosalicylic acid trimellitamide and acetyl 5-aminosalicylic acid trimellitamide.
 2. A composition according to claim 1 wherein the trimellitamide is of the formula ##STR6##
 3. A composition according to claim 1 wherein the polyphenylene ether is a poly (2,6-dimethyl-1,4-phenylene ether).
 4. A composition according to claim 1 wherein the amount of trimellitamide is about 2% to about 3% by weight based on polyphenylene ether present.
 5. A composition according to claim 1 wherein the polyphenylene ether has been melt processed under vacuum prior to reaction with the trimellitamide.
 6. A composition according to claim 5 wherein both the melt processing steps are effected by extrusion with vacuum venting.
 7. A composition according to claim 1 which has been melt processed at least once under vacuum after preparation.
 8. A composition according to claim 7 wherein the melt processing steps are effected by extrusion with vacuum venting.
 9. A composition according to claim 8 wherein about 2% to about 3% trimellitamide is employed, based on the polyphenylene ether present.
 10. A composition according to claim 1 wherein the trimellitamide is of the formula ##STR7##
 11. A composition according to claim 1 wherein the trimellitamide is of the formula ##STR8## 